Hullo all,

Can someone explain the following behavior to me? I would like to to create 
an extension of the field of rational functions in one variable 'y' over 
the finite field of three elements by adjoining a root of unity 'Y' and an 
element of Carlitz torsion 'X'. 

I run the following commands: 

sage: A.<y> = GF(3)[]; A
sage: w = polygen(A)
sage: K = Frac(A);K
sage: A1.<X> = K.extension(w^8 + (y^3 + y + 2)*w^2 + (y^2 + 2*y + 2)); A1
sage: B1.<Y> = A1.extension(w^2+2*w+2); B1

Note that 'w^2+2*w+2' is irreducible over GF(3), and 'w^8 + (y^3 + y + 
2)*w^2 + (y^2 + 2*y + 2)' is irreducible over 'A'. All fields are generated 
successfully. Trying to multiply 'X' and 'Y' or even 'y' and 'Y' then 
yields a NotImplementedError. This seems crazy to me, since by the output 
for 'B1', it knows it is an extension of 'A1', but it gets crazier. 

If instead I restart my worksheet and run:

sage: A.<y> = GF(3)[]; A
sage: w = polygen(A)
sage: K = Frac(A);K
sage: A1.<X> = K.extension(w^9 + (y^3 + y + 2)*w^3 + (y^2 + 2*y + 2)*w); A1
sage: B1.<Y> = A1.extension(w^2+2*w+2); B1

where I have multiplied through by 'w' in the modulus of 'A1', the 
extensions are generated correctly, and one may do arithmetic in all 
variables 'X', 'Y', and 'y'. 

I already have a workaround, but this behavior seems like a bug. So I 
thought I would ask. What's going on here?

All the best, Rudy

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